“Because sin is actions that harm us. Lying harms us. Abortion harms a woman – it’s a tremendous mental attack, and physical, sometimes. But we seem to get that muddled.

“In a way, thank God the Catholic Church does say we won’t allow it, because otherwise nobody’s saying that it’s a sin.”

In the interview, Irons also said it was a mistake for countries in the West to reject their Christian inheritance in favour of secularism.

He said: “Our society is based on a Christian structure. If you take those religious tenets away, then anything goes and it will become terrible – and you usually get into trouble.”

He continued: “Adultery might be very nice, but finally it ****s us up. And it ****s up the structure of society.

“We don’t steal – well, some people do – because it makes life intolerable for everybody.

“Yes, you can be in love and raise a family wonderfully by not being married, but actually marriage does give us a strength, because it’s quite hard to get out of, and so it makes us fight more to keep it together.

“If divorce becomes dead easy – which it sort of has – then we don’t have that backup because, for everybody, relationships are hard.”

Irons, who lives in Cork, Ireland, has raised his two sons by his second wife Sinéad Cusack, an Irish actress, as Catholics and occasionally he goes to church himself.

In 1986, he also played Fr Gabriel, a Jesuit priest in The Mission, the 1986 film directed by Roland Joffé, and from 2011 to 2013 he played the role of Pope Alexander VI in The Borgias, a television historical drama.

In 1990 he won an Oscar for best actor for his depiction of former Catholic Herald columnist Claus von Bülow in the film A Reversal of Fortune. He has also won several Golden Globes.

His remarks on abortion represent the latest controversial comments he has made on culture and morality.

In April 2013, he was critical of moves to legalise same-sex marriage, arguing that a legal redefinition could “debase” or change what marriage is.